What is False sharing?
A slowdown in which threads update different variables that happen to share a cache line, so the line bounces between cores.
Field: Multicore & Synchronization
False sharing in the explanations
The results are correct but performance drops sharply: this is false sharing.
Which describes false sharing in a multithreaded program?In multithreaded code, beware of false sharing, where separate variables in the same line cause cores to contend for it.
What is the typical size of a cache line (cache block) in m…The main obstacles to parallel speedup include parts that cannot be parallelized (Amdahl's law), waits on locks and barriers, cache lines bouncing due to shared data or false sharing, load imbalance and insufficient memory bandwidth.
Which is NOT a reason a parallel program fails to scale as …
Questions that mention False sharing (4)
- Which describes false sharing in a multithreaded program?
- False sharing occurs with an array of per-thread counters such as "long cnt[8];". What is the most suitable fix?
- What is the typical size of a cache line (cache block) in many current CPUs?
- Which is NOT a reason a parallel program fails to scale as cores are added?
Related terms
Cache line Spatial locality Speedup Amdahl's law ABA problem Acquire-release semantics Atomic instruction Barrier synchronization Bus snooping Compare-and-swap